create ion_4.19.h

system/core/libion/original-kernel-headers/linux/ion_4.19.h was
created manually and the following command was run to generate
system/core/libion/ion_4.19.h

bionic/libc/kernel/tools/clean_header.py
-ksystem/core/libion/original-kernel-headers/linux ion_4.19.h
> system/core/libion/ion_4.19.h

Test: make
Bug: 140916230

Change-Id: I2cd8cda903e77374cf85f38fe16a4e82156d5c67